The expansion of the swept volume of injected water by polymers in the porous medium is the main mechanism for polymer flooding to increase oil recovery.The transport of polymer and the oil displacement effect were investigated.Experiments have shown that there is no positive correlation between the viscosity of the polymer flooding agent and the oil displacement effect.The viscosity of the salt?resistant polymer (52.4 mPa?s) is higher than that of the "high?resolution" polymer (35.6 mPa?s ),but it has poor compatibility with the pore?throat structure of the reservoir and poor injection and shear resistance.The oil displacement experiments demonstrate that the overall recovery increase by salt?resistant polymer flooding (6.94%) is lower than that of "high score" polymer flooding (18.94%). Therefore, compared with the "high?score" polymer of "equal viscosity" or "equal concentration", the salt?resistant polymer has a worse ability to expand the swept volume.